منابع مشابه
Characterizations of Transversal and Fundamental Transversal Matroids
A result of Mason, as refined by Ingleton, characterizes transversal matroids as the matroids that satisfy a set of inequalities that relate the ranks of intersections and unions of nonempty sets of cyclic flats. We prove counterparts, for fundamental transversal matroids, of this and other characterizations of transversal matroids. In particular, we show that fundamental transversal matroids a...
متن کاملTransversal Lattices
A flat of a matroid is cyclic if it is a union of circuits; such flats form a lattice under inclusion and, up to isomorphism, all lattices can be obtained this way. A lattice is a Tr-lattice if all matroids whose lattices of cyclic flats are isomorphic to it are transversal. We investigate some sufficient conditions for a lattice to be a Tr-lattice; a corollary is that distributive lattices of ...
متن کاملCongenital total eversion of the upper eyelids.
Eight cases of bilateral and 6 cases of unilateral congenital total eversion of the upper eyelids are reported here. It is suggested that an appreciable overlapping of the lower eyelid margin by the upper eyelid is a predisposing factor in the mechanism of eversion in this condition. Treatment by injection of hyaluronidase into the chemotic conjunctiva followed by placement of a lid suture to r...
متن کاملUpper Bounds on the Total Domination Number
A total dominating set of a graph G with no isolated vertex is a set S of vertices of G such that every vertex is adjacent to a vertex in S. The total domination number of G is the minimum cardinality of a total dominating set in G. In this paper, we present several upper bounds on the total domination number in terms of the minimum degree, diameter, girth and order.
متن کاملAn upper bound for the transversal numbers of 4-uniform hypergraphs
The main purpose of this paper is to prove that if H is a 4-uniform hypergraph with n vertices and m edges, then the transversal number r(H) <2(m +n)/9. All standard terminology of hypergraphs is from [ 11. Suppose H = (V, E) is a k-uniform hypergraph with n vertices and m edges. Tuza [2] proposed the problem of finding an upper bound for the transversal number r(H), of the form t(H) < ck(n + m...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: HPB
سال: 2020
ISSN: 1365-182X
DOI: 10.1016/j.hpb.2020.04.294